The present invention relates to a developing agent and a method of manufacturing such a developing agent.
Conventionally, a so-called mechanical pulverizing method is generally used for manufacturing a color developing agent, as in the case of the monochrome developing agent manufacturing method. In the mechanical pulverizing technique, first, a binder resin and a pigment are fused and mixed together and the mixture is kneaded, and then the kneaded material is subjected to pulverizing and classifying, thus obtaining toner particles. Further, an additive is added to thus obtained toner particles, and thus a developing agent is obtained. However, when the mechanical pulverizing method is applied to manufacture of a color developing agent, it is required to clean the manufacturing equipment parts each time when they are used to manufacture a developing agent of a different color. In particular, the cleaning of the kneading device and pulverizing and classifying device is very complicated due to the structures of these devices, thus requiring a great amount of time. For this reason, the manufacture of a color developing agent has a low productivity, and involves a high production cost, as compared to the case of the monochrome developing agent.
In order to bring a solution to these drawbacks, there has been recently proposed such a technique that colorless toner particles which do not contain a pigment are prepared and the pigment is attached onto the surfaces of the colorless toner particles. According to this technique, those steps from the fusing and kneading step for toner materials to the pulverizing and classifying step can be carried out in batch for manufacturing developing agents of any colors. Therefore, the time required for cleaning the kneading device and pulverizing and classifying device, can be shortened, thus making possible to enhance the productivity. Thus, it becomes possible to provide a more inexpensive color developing agent.
However, the pigment is in the form of solid secondary aggregate, and therefore it is conventionally difficult to sufficiently disperse it when it is attached onto the surfaces of colorless toner particles by dry-type mixture using a mixer or the like. Therefore, the color developing agent obtained by this method entails drawbacks such as a low dispersibility of the pigment, a low chromatic saturation, a narrow color reproduction range, a low transparency and the like.
The first object of the present invention is to provide a method of manufacturing a developing agent which has a high pigment dispersibility, and which can achieve a high transparency and a high color reproducibility at low cost, particularly when a color developing agent is manufactured.
The second object of the present invention is to provide a developing agent which has a high pigment dispersibility, and which can achieve a high transparency and a high color reproducibility at low cost, particularly when a color developing agent is manufactured.
According to the first aspect of the present invention, there is provided a method of manufacturing a developing agent, comprising:
a wet-type mixture step for mixing colorless toner particles containing a binder resin and a pigment wetted in advance, together in a wet-mixture manner, thereby obtaining wet toner particles; and
a drying step for drying the wet toner particles, thereby obtaining toner particles.
According to the second aspect of the present invention, there is provided a developing agent comprising toner particles obtained by mixing colorless toner particles containing a binder resin and a pigment wetted in advance, together in a wet-mixture manner, thereby obtaining wet toner particles, and drying the wet toner particles.
In the manufacture of the developing agent of the present invention, colorless toner particles which do not contain pigments are prepared, and then the particles are mixed with pigments. With this manufacturing structure, up to the preparation of toner particles, those steps can be carried out in batch without having to clean the part devices regardless of the color of the developing agent, thus making it possible to enhance the productivity and lower the production cost.
Further, in the present invention, a pigment which is easily secondary-aggregated when dried is mixed in a wet manner with the colorless toner particles before being dried, and therefore the dispersibility of the pigment in thus obtained toner particles becomes very high. Therefore, the present invention can provide a developing agent having an excellent color reproducibility and a high transparency.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be leaned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.